Thermodynamic cyclic process

ABSTRACT

A thermodynamic cyclic process with a gaseous working medium, which is alternately compressed and expanded, in which process a working medium is employed, which experiences a volume expansion due to chemical processes at the higher temperature after the compression and a corresponding volume contraction at the lower temperature after the expansion, is to be improved so that a higher efficiency is achieved. This is achieved in that the volume contraction is endothermic. In this case, the cyclic process can increase the efficiency both in heat engines and also in heat pumps.

This is a continuation of copending application Ser. No. 07,294,560filed on Dec. 9, 1988 now abandoned.

The invention relates to a thermodynamic cyclic process with a gaseousworking medium which is alternately compressed and expanded, in whichprocess a working medium is employed, which experiences a volumeexpansion due to chemical processes at the higher temperature after thecompression and a corresponding volume contraction at the lowertemperature after the expansion.

In cyclic processes there exists, quite generally, the problem that theyhave a limited efficiency. This efficiency is, on the one hand, given byphysical laws, but on the other hand, also determined by constructionaldetails. Thus, for technical reasons, it is in most cases only possibleto operate these devices with a relatively low efficiency.

A certain increase in the efficiency is to be aimed at in a process ofthe initially mentioned type (UK-A2,017, 226). In the cyclic processdescribed therein, for the generation of energy, the thermal energywhich is supplied is not only employed for expanding the gas due to theheating in the conventional manner. Rather, further heat is expended inorder to liberate further gas on account of an endothermic chemicalprocess, i.e. to bring about a further volume expansion. The advantagethat more working gas is obtained at the higher temperature is, however,counteracted by the disadvantage that more heat is also given off to thecolder heat reservoir in the course of the corresponding exothermicvolume contraction at the lower temperature of the circuit.

The object of the invention consists in providing a cyclic process ofthe initially mentioned type, which process has a very high efficiency.

The object is achieved, according to the invention, in that the volumecontraction is endothermic.

In contrast to the previously known cyclic process, there is thus noneed for additional energy to be expended in order to obtain theadditional gas. Rather, the appropriate chemical processes involved inthe formation of the additional gas at the higher temperature areexothermic, so that these processes run automatically, as soon as thegas has actually been brought to the appropriate temperature. Thus, in aheat engine less heat needs to be supplied at the higher temperature,whereby the efficiency is increased. On the other hand, less energy alsoneeds to be given off to the heat reservoir of lower temperature at thelower temperature, since the corresponding volume contraction isendothermic, which leads to a further increase in the efficiency. It iseven feasible that, in this case, heat is absorbed from the environmentat the lower temperature.

If the cyclic process is employed for a heat pump, then there islikewise an increase in the efficiency. In the heat pump, heat iswithdrawn from a temperature reservoir of lower temperature and givenoff, by means of mechanical energy, to a temperature reservoir of highertemperature. Because of the endothermic chemical volume contraction,more heat is absorbed at the lower temperature from the environment.With an equal quantity of mechanical energy to be expended, more heat istherefore gained, and the efficiency therefore rises.

One possibility for implementing the cyclic process would be, forexample, to employ a molecular gas, the molecules of which decompose atthe higher temperature into individual components, in the extreme caseinto individual atoms. Another possibility consists, as will be statedbelow, in heating a metal powder which absorbs or has adsorbed a gas.

Because of the fact that the working medium occupies a greater volume atthe higher temperature, the gas is able to perform more work than wouldotherwise be the case. At the lower temperature, the chemical reactionand/or the desorption processes then proceed in the other direction,i.e. as absorption or adsorption processes, so that the gas againoccupies its normal volume and is then once again available for thecycle.

Since the working medium employed is one which heats up in the course ofthe volume expansion at the higher temperature, in the case of a heatengine the quantity of heat supplied can be kept very small. Thissignifies a considerable saving of energy.

In an advantageous embodiment, the chemical process is anadsorption/desorption process.

In a particularly advantageous embodiment, in this case theadsorption/desorption of at least a part of the gaseous working mediumtakes place at surfaces which are alternately brought into contact withthe gas at the higher and the lower temperature.

The surfaces may be disposed on a circular disc, which extends into thegas volumes of higher and lower temperature and is rotated. The disccould, for example, consist of a plurality of sectors, the gas of highertemperature then flowing through sectors, for example, above the axis ofrotation, while the gas of lower temperature flows through sectors belowthe axis of rotation. In this case, it must, of course, be ensured bymeans of appropriate sector walls that, in this case, the gas of higherpressure does not flow through simultaneously over or through thecircular disc to the region of lower pressure of the cyclic process.

Instead of this embodiment, it can also be provided--which has likewiseproved to be advantageous--that the working medium consists of twocomponents, which do not react with one another chemically and one ofwhich is a normal gas and the other of which experiences the volumeexpansions/volume contractions due to chemical reactions and/ordesorption processes. Both types of chemical reactions can, of course,also be combined with one another.

In a mixture of two components, the working gas which does notparticipate in the chemical reactions has the function of serving astransport means for quantities of heat and/or a metal powder which isguided round together with the gas in the circuit and at which theadsorption/desorption takes place.

Both in the cases in which the metal causing the adsorption/desorptionis disposed on a disc and also in the cases in which the metal is guidedalong in the form of a powder in the gas stream, the gas can behydrogen. Platinum, palladium or other catalyst metals which can absorbhydrogen can be employed as the metal.

If the cyclic process is employed for a heat engine, then it canadvantageously be further provided that the expansion engine isconnected to an electrical generator. This generator then deliverselectrical energy in place of mechanical energy. At least a part of theheat energy for the heating vessel can, in this case, be delivered bythe generator. In particular in circumstances in which the gas is veryintensely heated in the course of the volume expansion due to chemicalreactions and/ or desorption processes, it would even be possible toendeavour to have the heat energy delivered entirely by the electricalgenerator. In many other cases it will, however, be simpler to use, forthis purpose, heat sources which are already in existence.

Advantageously, furthermore, the parts of the circuit of the workingmedium are provided with surfaces which promote or intensify thereactions leading to the volume expansions/volume contractions. Inparticular, the heating vessel and the heat exchanger or parts thereofcan be provided with such surfaces.

The heat exchanger can undertake the heat exchange with the air of theenvironment. However, a heat exchange with a quantity of water is alsopossible; for this purpose, pumps must then be provided for the water,if required. However--and this can prove to be expedient in certainextreme situations--it is also possible, in order, for example, to avoidan excessively low temperature of the working medium in the heatexchanger, initially to compress the air which is conducted from outsidevia the heat exchanger, whereby that air is heated. The exhaust air canthen be conducted via an expansion engine, so that the energy employedfor increasing the pressure of the ambient air is regained, at least inpart. In this way, the efficiency of the entire device can be increasedfurther.

The invention is described in the text which follows, with the aid of anadvantageous embodiment, with reference to the accompanying drawings. Inthe drawings:

FIG. 1 shows, in a diagrammatic representation, the construction of aheat engine which operates in accordance with the cyclic processaccording to the invention;

FIG. 2 shows a P/V diagram to explain the mode of operation of theengine of FIG. 1;

FIG. 3 shows, in a diagrammatic representation, the construction of aheat pump which operates by the cyclic process according to theinvention; and

FIG. 4 shows another heat engine which operates in accordance with theprocess according to the invention.

In the engine shown in FIG. 1, the gaseous working medium is in thefirst instance compressed in a compressor 1, and then passes in thedirection of the arrow into the heating vessel 2. This heating vesselcontains a heating element, which is indicated at 3 and which is heatedby a heat source 4. The heating element 3 could, of course, also be theouter wall of the vessel 2; in many cases, a separate heating element 3will, however, be employed, for example in the case of electricalheating.

The working medium, already heated by the compression, is conductedthrough the upper part of a disc-shaped element 20, which is permeableto gas in the axial direction. On the other hand, however, a gasmovement in the circumferential direction is very greatly obstructed, ifnot even made entirely impossible, by appropriate sectors on thedisc-shaped element 20. Moreover, the disc-shaped element 20 issurrounded by a housing, so that all gas which is conducted into thedisc-shaped element on one side actually flows out again on the otherside. The disc-shaped element is now provided with a finely dividedpowder, onto which hydrogen gas is adsorbed. The metal powder can, forexample, in finely divided form, be disposed on a silicone foam. Metalpowders which are particularly suitable in this case are those whichcool down to a particular extent in the course of the adsorption ofhydrogen and heat up in the course of the desorption of the hydrogen.Moreover, they should bind the greatest possible quantity of hydrogen.

Since the temperature of the gas is increased by the heat source 3, thehydrogen gas is now given off from the metal powder. Accordingly, moregas is available, which is expanded in the expansion engine 5 and thusdoes mechanical work. Moreover, as a result of the exothermic process,there is also a further heating of the working medium, which nowconsists of the original gas and hydrogen.

Downstream of the expansion engine 5, the expanded gas or other workingmedia are conducted via a regulating valve 6 into a heat exchanger 7, inwhich the heat exchange with the environment takes place, so that thegas again adopts its original temperature.

In this process, the gas is conducted through the heat exchanger 7 manytimes. Previously and afterwards, it is conducted many times through thelower region of the disc 20. Since the disc 20 has meanwhile beenrotated, the metal in this lower region is in the first instance freefrom hydrogen. At this point, the hydrogen is again adsorbed, and thistakes place with simultaneous cooling of the working gas since theadsorption is endothermic. In this way, less energy is given off to theenvironment or, in the most favourable case, thermal energy is evenabsorbed from the environment. In this way, a very high efficiency isachieved.

Subsequently, the gas can then be compressed again in the compressor 1.

The heat exchange with the environment is also assisted by a ventilator8, which is driven by a motor 9.

Compressor 1 and expansion engine 5 are disposed on a common shaft 10,so that the compressor, after a once-only start, can be driven by thecircuit itself, i.e. by the expansion engine 5. The mechanical energywhich is available in addition can be absorbed by a generator 11, a partof the electrical power of which is conducted via lines 12 to the motor9 for the ventilator 8. Another part of the energy can be usefullywithdrawn at 13. In addition to this, or in place of this, mechanicalenergy can also be extracted at 14 from the shaft 10.

In the figure, it is also shown that the shaft 10 also rotates the disc20. In this case, however, the disc 20 will normally be rotated at alower speed than the compressor 1, the expansion engine 5 and thegenerator 11. For this purpose, a reducing gear not shown in the figurewill also be provided.

The mode of operation is now to be illustrated with reference to thediagram of FIG. 2. The original, hydrogen-free working medium iscompressed in the compressor 1 in the portion 1-2 in the P/V diagram andpasses into the heating vessel 2. In the heating vessel, heat issupplied to the gas through the heating element 3, whereby the volume isexpanded while the pressure remains constant (portion 2-3 in the P/Vdiagram). Hydrogen gas is now released in the disc-shaped element 20,while energy is given off (portion 3-3' in the P-V diagram). At point 3'of the P-V diagram there is thus a working gas, which consists of theoriginal gas (volume at point 3) and the hydrogen gas, which at point 3in the first instance has a volume 0 and at 3' has its actual volume.The P-V diagram therefore shows the sum of the two gas volumes.

The original working medium and hydrogen are then expanded, in such away as to do work, in the expansion engine 5 (portion 3'-4' in the P-Vdiagram); in this case, mechanical work is done.

Subsequently, the adsorption of the hydrogen gas then takes place in thelow-pressure and low-temperature region of the disc-shaped element, withthe absorption of heat (portion 4'-4 in the P-V diagram). Only theoriginal working gas must then also be cooled (portion 4-1 in the P-Vdiagram). This heat can be absorbed, at least partially, by theendothermic process of the hydrogen adsorption. Subsequently, the gashas then again reached its original condition (point 1); the cyclicprocess can begin afresh.

FIG. 3 shows a heat pump which operates in accordance with the cyclicprocess according to the invention. In principle, the heat pump of FIG.3 differs from the heat engine of FIG. 1 only in that, in place of theheating vessel 2, heating element 3 and heat source 4, a heat exchanger21 is provided, by which a medium to be heated (for example the air inthe room) is heated.

In operation, the shaft 10 of the heat pump of FIG. 3 is driven byelectrical energy fed in at 13 by means of the motor/generator 11 or bymechanical energy applied at 14. The gas is compressed in the compressor1 and thereby is heated. In the disc-shaped element 20, in consequenceof desorption of hydrogen more gas is obtained. The heat is given off,in the heat exchanger 21, to the medium to be heated. After partialrecovery of energy in the expansion engine 5, the hydrogen component ofthe gas is adsorbed in the lower part of the disc-shaped element 20 withthe absorption of heat. Moreover, heat is absorbed at this point, sincethe gas cooled by the expansion must be heated again for the circuit.The corresponding heat is extracted from the environment in the heatexchanger 7.

In the heat engine shown in FIG. 4, the disc-shaped element 20 has beendispensed with. In place of this, a metal powder is entrained in the gascircuit. The exothermic desorption of hydrogen gas, accompanied by avolume expansion of the working medium, takes place, in this embodiment,in the heating vessel 2. Original, neutral working gas, hydrogen andmetal powder are then also carried along in the circuit, until, in theheat exchanger 7, the hydrogen gas is again adsorbed by the metal powderin an endothermic process. However, the advantages of the exothermic andendothermic processes, as well as of the corresponding volume expansionsand volume contractions continue to be obtained in their entirety. Adisadvantage is simply that metal powder must be entrained in theworking medium; this may lead to wear phenomena at the walls of thelines, of the compressor and of the expansion engine.

The amazing increase in the efficiency may also be explained by the factthat the hydrogen is `compressed` in the course of the circuit withoutadditional expenditure of energy by the adsorption, to the volume 0.

I claim:
 1. A thermodynamic cyclic process with a gaseous working mediumthat is compressed with an associated temperature increase to a hightemperature and secondarily expanded with an associated temperaturedecrease to a low temperature, the working medium experiencing a firstvolume expansion due to chemical processes resulting in an increase inthe number of gaseous molecules at the high temperature after thecompression but before the secondary expansion and a correspondingvolume contraction due to a decrease in the number of gaseous moleculesat the low temperature after the secondary expansion but before thecompression, wherein an endothermic chemical process occurs during thevolume contraction.
 2. Cyclic process according to claim 1,characterized in that the chemical process is an adsorption/desorptionprocess.
 3. Cyclic process according to claim 2, characterized in thatthe adsorption/desorption of at least a part of the gaseous workingmedium takes place at reaction surfaces which are alternately broughtinto contact with a flow of the gas at the high and the low temperature.4. Cyclic process according to claim 3, characterized in that thereaction surfaces are disposed on a circular disc which is rotated intothe gas flow of high and low temperature.
 5. Cyclic process according toclaim 1, characterized in that a gaseous working medium is employedwhich consists of two components which do not react chemically with oneanother and one of which is a normal gas and the other of whichexperiences the first volume expansion and the endothermic volumecontraction due to the chemical process.
 6. Cyclic process according toclaim 1, characterized in that a mixture of a gas and a powder isemployed as the working medium which experiences the first volumeexpansion and the volume contraction due to the chemical process. 7.Cyclic process according to claim 6, characterized in that a metalpowder is employed as the powder.
 8. Cyclic process according to claim5, characterized in that hydrogen is employed as the other component. 9.Cyclic process according to claim 1, characterized in that the cyclicprocess is operated so that the step of compressing includes heating themedium to the high temperature with mechanical energy and is preceded bythe step of heating the medium by the cooling of a thermal reservoir oflower temperature.
 10. Cyclic process according to claim 3,characterized in that the reaction surfaces are provided with surfaceswhich promote or intensity the chemical process.
 11. Cyclic processaccording to claim 1, characterized in that, on a lowering of thetemperature of the working medium below the ambient temperature, thermalenergy is absorbed from the environment through a heat exchanger. 12.Cyclic process according to claim 1, characterized in that a mixture oftwo gases, at least one of which is synthetically produced and acts onthe other in the manner of a catalyst, is employed as the working mediumwhich experiences the volume expansion due to the chemical process. 13.Cyclic process according to claim 2, characterized in that a mixture ofa gas and a powder is employed as the working medium which experiencesthe volume expansions due to chemical reactions and/or desorptionprocesses.
 14. Cyclic process according to claim 5, characterized inthat a mixture of a gas and a powder is employed as the working mediumwhich experiences the volume expansions due to chemical reactions and/ordesorption processes.
 15. A thermodynamic cyclic process which uses agaseous working medium that is alternately compressed with an associatedpressure and temperature increase and expanded with an associatedpressure and temperature decrease, comprising the steps of:(a) selectinga working medium that is in an inert state within a known,pressure-volume envelope of the process and which undergoes a firstchemical process including expansion at a first known pressure-volumecondition outside said envelope and undergoes an endothermic secondchemical process including contraction to an inert state at a secondknown pressure-volume condition outside said envelope, the expansionincluding an increase in the number of gaseous molecules and thecontraction including a decrease in the number of gaseous molecules; (b)directing a flow of said working medium in a closed loop which includesa reference location where the medium is in a reference state withinsaid envelope and at a reference temperature that is the minimumtemperature of the cyclic process; (c) compressing the working mediumadiabatically from the reference state so that the temperature of themedium rises to a maximum value while the pressure and volume are withinsaid envelope; (d) after step (c), adding heat to the medium until thefirst chemical process occurs at said first condition outside theenvelope, whereupon the medium experiences an expansion as a result ofthe chemical process; (e) after step (d), extracting useful work byexpanding the medium adiabatically to a maximum volume outside saidenvelope; (f) after step (e), withdrawing heat from the medium until thesecond chemical process occurs at said second condition, whereupon themedium experiences a contraction to a pressure and volume conditionwithin the envelope, as a result of the second chemical process; (g)further cooling the medium to said reference state; and (h) cyclicallyrepeating steps (c)-(g).
 16. The cyclic process of claim 15, wherein thestep of selecting a working medium includes selecting a medium whichundergoes the first and second chemical processes by adsorption anddesorption.
 17. The cyclic process of claim 15, wherein the step ofselecting a working medium includes selecting a medium which consists oftwo components which do not react chemically with one another and one ofwhich is a normal gas and the other of which experiences the volumeexpansion and the endothermic volume contraction as a result of thechemical processes.
 18. A thermodynamic cyclic process which uses agaseous working medium that is alternately compressed with an associatedpressure and temperature increase, and expanded with an associatedpressure and temperature decrease, comprising the steps of:(a) selectinga working medium that is in an inert state within a known,pressure-volume envelope of the process and which undergoes a firstchemical process including expansion at a first known pressure-volumecondition outside said envelope and undergoes an endothermic secondchemical process including contraction to an inert state at a secondknown pressure-volume condition outside said envelope, the expansionincluding an increase in the number of gaseous molecules and thecontraction including a decrease in the number of gaseous molecules; (b)directing a flow of said working medium in a closed loop which includesa reference location where the medium is in a reference state withinsaid envelope and at a reference temperature that is the minimumtemperature of the cyclic process; (c) compressing the working mediumadiabatically from the reference state until the state of the medium isoutside the envelope, whereupon the exothermic chemical process occursand the medium experiences the maximum temperature of the cyclicprocess; (d) after step (c), drawing away useful heat from the medium;(e) after step (d), expanding the medium to the maximum volume of thecyclic process to perform useful work whereby the medium reaches theminimum temperature of the cyclic process in a state outside saidenvelope; (f) after step (e), adding heat to the medium while the mediumis contracting to the reference state as a result of the endothermicsecond chemical process; and (g) cyclically repeating steps (b)-(f). 19.The cyclic process of claim 18, wherein the step of selecting includesselecting a gaseous medium that undergoes an adsorption and desorptionchemical process.
 20. Cyclic process according to claim 1, wherein theworking medium is compressed in a compressor, heated in a heatingvessel, expanded in an expansion engine, and cooled in a heat exchangerwhich exchanges thermal energy with the environment.